Penetration studies of clotrimazole from semisolid formulation using step-scan FT-IR photoacoustic spectroscopy

Purpose. The aim of this study was to elucidate the potential use of the step-scan FT-IR photoacoustic spectroscopy (PAS) for the nondestructive determination of drug penetration into membranes. Methods. The penetration of clotrimazole from a 10% (w/w) suspension in Vaseline(R) into a dodecanol-collodion acceptor membrane was studied by three methods: the step-scan FT-IR PAS with a phase modulation, a multilayer membrane system, and a modified libration model. Based on Fick's second law, the diffusion coefficient of the drug in the membrane was derived by numerical fitting of the experimental data. Results. The three methods applied provided almost the same diffusion coefficient D = 2.2 10(-9) cm(2)/s for clotrimazole in the membrane. Because of the non-destructive mode of operation, the accuracy of results obtained by FT-IR PAS is much better than that attainable by other two methods. Conclusions. Step-scan FT-IR photoacoustic spectroscopy in conjunction with a phase modulation is useful to determine the penetration of drug through membranes. The fact that samples can be investigated without elaborate preparation is an advantage of this spectroscopic technique.